I have a low serial number Krag that I took out of the safe the other day to prep for winter. My new endoscope camera revealed a much better than anticipated bore, better than even my low round count Shilen Select Match 308 barrel.

Almost no firecracking, perfect lands and grooves, very few rust pits. But after cleaning two 308's, I tried to put the same jag and patch down the Krag to oil the bore, and it would not fit! I had to drop down a jag size, and that confused me.

Is the 30-40 bore smaller than the 308 Win?

The first Krags had an issue with bore size variation. My recollection is not perfect on this but I think most were too large and many of these work better with cast bullet sized a little on the large size.
Later Krags should have been held to a tighter tolerance, and should have a .300 bore and .308 land to land measurement just like your Shilen.
No copper fouling buildup?

Yes, it does copper foul a bit, but I've not put more than about 30 rounds down it since I started shooting it, but it shoots very well. 

It's serial number 133937 and professionally sporterized probably sometime in the 20's. Was purchased around 1940 from a pawn shop by my Dad.

I don't recall him ever shooting it when I was young, and I put one round down it about 1969 during a pig hunt. It sat until 2015 when I shot it again, and bought dies for hand loading.

'Texas10' - Your Krag, #133937, was assembled around October, 1898. Therefor, it is not really a "low number" Krag.

What is your barrel length? Both model 1898 carbines and rifles are found near your Krag's serial number.

If you 'slugged' your bore (with a soft lead oversize slug), you could easily measure your bore's land and groove diameter.

FWIW - I have generally found my model 1898 Krag barrels to run about .3085 to .3095 inches in groove diameter.

My rifles in .30-06 and .308 Winchester & NATO calibers have 'tighter' bores.

My Krag barrels shoot .308" diameter commercial jacketed bullets well.

If you are going to shoot cast bullets, it is important to know your actual bore dimensions. Cast bullet shooters generally use projectiles sized .001" or .002" over barrel groove diameter.

Most of us would enjoy seeing photos of your 'Family Krag'.

Thanks, Butler,

I'll take some photos and post. I actually did post some when I first started down the Krag road back in 2015. My pics are still on the sporterized page. I just looked them up.

Two years ago I took my first deer with it, on the 75th anniversary of when my dad took a deer on the family farm in Oregon during Christmas leave from the Army. He'd just bought the gun at a pawn shop in Waco, TX. I have a pic of him standing with the deer, Krag by his side.

I've got some Hornaday 220 gr. RN, and a bunch of different powders, so I won't be casting my own.  I'll chase up some Hornaday brass and see if I can load some rounds that shoot as well as the factory loads I have.

I would like to learn to use the elevation adjustment on the peep. Last time I tried, I sent one over the berm at 500 yds and I don't want to repeat that experience.  :o

One nice thing about the serial number and manufacture date is it isn't classified as a firearm.  8-)

The barrel on my 1901 Model '98 Krag, slugs at .309"  It shoots all factory and handloaded ammo using .308" bullets just fine. 

Any links for "how to slug a barrel" would be appreciated. Bore looks mighty fine using my new Teslong bore scope.

The easier way to do it is to take a pure, round soft lead fishing weight and insert it into the chamber of your Krag. Then tap it with a wood dowel slightly smaller in diameter than your bore to push it into and down the length of the bore. When it taps out the muzzle, you will have a resized lead weight that reflects the smallest diameter of the bore that it traveled down. If you drip a little oil on the weight before tapping it down the bore, it'll go a little easier.

One disadvantage of this approach is if your bore is pitted bad, it will chew up the lead weight a lot before it drops out the muzzle. It will also leave behind small chunks of lead in the pitted areas, similar to shooting a cast bullet in a badly pitted bore.

I use a Hawkeye Bore Scope. That was the best investment I have ever made for my gun collection. I love looking into bores before and after cleaning. Really teaches you what works and what doesn't work with cleaning your guns. Also it's irreplaceable for examining older military firearms for bore condition and damage.

I have done the lead weight approach but now I use Cerrosafe to make an actual casting of my chamber that gives me measurements I need for reloading. Each chamber can be slightly different. But, it's a good and safe way to get a lot of info about your rifle or carbine.

Brownell's sells Cerrosafe. It melts at a real low temperature and hardens quickly. Safe to use.

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Nix on the "fishing weight".  Those things are made of unknown alloy, including scrap with plenty of scratchy contaminants. Use something intended to be passed through a gun barrel, like buckshot.

And while a wooden dowel is OK for starting the slug the first couple of inches, NEVER attempt to drive a slug all the way through with wood - which can split, splinter, and wedge itself most horribly! Use a smooth solid steel rod with a flat face for pushing the slug through.

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Ok now, that was just too easy! OO buck, an Oak dowel, and a stiff cleaning rod perhaps?

What are the dimensions I'm looking for? Groove and bore?

The barrel looks beautiful inside, so this should be a piece of cake.

Texas10 wrote on Dec 21^st, 2019 at 1:53am:

Ok now, that was just too easy! OO buck, an Oak dowel, and a stiff cleaning rod perhaps? What are the dimensions I'm looking for? Groove and bore? . . .

Bamboo chopstick makes handy starter. Best is a brass rod about 7mm.

Nominal US Krag barrel is .300"x.308" - some a bit larger, few smaller.

Slugging it was a walk in the park. OO buck measured .300 across the lands, and .306 in the grooves. However across one set of grooves, it measured .301.

Any comments welcome.

.301" or .306" groove diameter is likely incorrect. Clean bore thoroughly, grease bore and new buckshot, try again. Use micrometer if available. Be gentle when taking readings. Shot is soft, requiring light touch.

Is your Krag barrel an original Springfield Armory barrel? Has it been changed on your Krag? Pictures might help. Might not be original and measurements might be different than expected.

Just a thought.

I like Parashooter's advice on this, I am thinking the round shot rocked a little going through the bore. Make sure the rod you use to push the slug through is flat and square on the end. Using a file and square can accomplish this.
Two other less likely possibilities are some of the grooves in the barrel are filled with copper alloy which would be a little harder than lead or a rough spot in the bore scrapped off some of the lead.

If the .301 measurement was real you would barely be able to see the rifling in the barrel .0005 per side would nearly be invisible. The fact that the .301 measurement is probably so wrong makes your .306 measurement suspect also which is a good thing now.

You may be right. I used the method described above using a 00 buckshot. I lubed the shot with Hobo Oil and wiped the excess off before driving into the muzzle. I was surprised as to how easy it was to push out after it was about 4 inches down the barrel.

I performed this twice. The first time the shot came out distorted, so I tossed it and tried again.

I'll try it again and select a better looking, less distorted shot I've pulled from a 12 ga shell. I have the exact same micrometer pictured, and have standards I've check accuracy with.

May do a few other barrels too.

I repeated the slugging process and confirmed that the bore is .300 and grooves are .306 to .3065

If it is supposed to be .308 I guess this would explain my first observation that a jag and patch combination that worked well in my 308, but does not fit into the krag, is due to the bore being slightly smaller.

Unless it's been answered and I missed it, I'll ask again. Are you sure that this is an original barrel on your Krag? Many have been changed. You can't always tell from the front sight base.

Nothing wrong with a smaller groove diameter, if indeed that's what you have.  I very regularly shoot .308 bullets out of my Swiss K31.  It has a .294" bore and .3055" groove diameter and is perhaps the most accurate milsurp rifle I have.  The bullets will swage down to the diameter they need to, once the pressure starts rising.  I generally anchor the push out rod to the floor and hit the rod I'm pushing the ball in with so that the ball is smushed out into the grooves, making sure you get the full diameter.  You ought to be getting the full diameter with the .33" OO.

@Whig,

Although I have no reason to suspect an aftermarket barrel was fitted at one time, because it's been sporterized there remains the possibility that it has. What I can tell you is that the blued barrel is 22 inches long, and a Pacific front sight soldered on. Bluing was removed for that work and was not replaced. The sight is clocked slightly to port.

There are two holes, drilled and tapped on the top of the barrel, and a dove tail machined into the barrel for an iron sight, but has been filled with lead.

There are stamped marks on the breech consistent with what I've read.

I shot it today at 100 yds using handloads consisting of new Winchester brass, CCI 200 primers, 40 grs of IMR 4350 and 220 gr Hornaday round nose, and it shot well putting 5 in the 10 ring once I got used to the peep sight.

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@Madsenshooter,

The 00 buckshot ball got shaved a bit being forced into the muzzle, with a ring of lead hanging off the rear as it was tapped down 3 inches or so. Wise to the issue of rotation now, I made sure it was driven out carefully, which by the way, was quite easy to do. Easy push with a hardwood dowel.

Barrel was clean and oiled for the test.

Cleaning today after range time, I once again found differences in patch/jag size compared to my 308 barrels, but finding a good patch combination to produce a tight fit was not a problem.

Cleaning with Ed's Red first, to be followed with a borescope examination for copper.

Thanks for the info and pictures. I have never seen those markings on a Springfield Armory barrel- the numbers on the chamber face of the barrel. It also looks to have an old dovetail cut behind the rear sight screw holes. I suspect it is not an arsenal barrel and may have been made with slightly different bore rifling cuts. That could answer the unusual measurements you got.

It's great to hear, though, that you are getting it to shoot well. Lots of fun with a Krag in almost any condition!

Keep up the good work.

Almost forgot to post pic of target. IF there's no pic, it didn't happen. ;)

This shot closest to center of bull was from previous 3 rounds while I adjusted windage on the Peep.

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Promising group! Now go shoot more of them and stop 'futzing' like a Bench Rest Shooter.

FWIW - An original Krag barrel will have an 'index mark' at the "9 O'clock" position and a "P" (proof) mark.

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I pulled the action from the stock to look for any proof stamp, but did not fine one.

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Here is what I did find, a letter I and an O.

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I am also including a pic of the inspector stamps on the action

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Texas10:

FWIW - I believe your barrel is an original Krag barrel, (with some alterations - shortened, commercial front-sight, and 'dovetailed' at one time for a commercial rear-sight).

I think the "I", on your barrel, may actually be a poorly stamped "P". Your action and barrel reveal armory index marks.

I played a bit with you photos:

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Looks original to me, that's for sure a poorly struck P.